The present invention relates generally to speed changers of the kind comprising two pulleys, driving and driven respectively, each of which comprises a hub and two annular flanges facing each other around the said hub to receive a belt, one of the flanges being axially movable relative to the hub and being subjected to the action of annular elastic means which urge it continuously towards the other flange, which is fixed, these elastic means bearing against the movable flange and a bearing piece fixed to the hub.
For controlling the configuration of the assembly and thus the transmission ratio, the movable flange of at least one of the pulleys is subject to the action of elastic return means which urge it continuously towards the fixed flange, and which comprise an annular piece with a variably conical shape known as a diaphragm, which through a peripheral part forming a Belleville washer, bears axially indirectly on the movable flange and which, through a central part divided into radial fingers, bears indirectly on the axially fixed bearing piece of the hub.
A speed changer of this kind is described in U.S. Pat. No. 4559026.
In this document, between the diaphragm 21 and the bearing piece fixed to the hub, to constitute a rocking axial bearing, a bridging element made of resilient material is fixed both axially and circumferentially, on the one hand to the inner peripheral part of the diaphragm and, on the other hand, to the bearing piece. For this purpose the bridging element is glued or fastened to the diaphragm and to the bearing piece.
A bridging element interposed in this way between the diaphragm and the movable flange, and its method of assembly, present disadvantages.
Amoung these disadvantages must be mentioned the operations of fastening or glueing, which are lengthy and delicate, and consequently have a relatively high cost.
The invention aims to reduce these disadvantages whilst ensuring a reliable connection between the diaphragm and the movable flange to ensure a good transmission of torque.